This invention relates to a decelerator for use in roller blinds of the type having a spring-motor to wind up a screen on a tube.
The spring-motor type roller blind is desirably equipped with a decelerator to reduce the screen-winding speed to the extent that the screen is always wound up at moderate speeds even if it is fully payed out and then released. Otherwise, it is caused to rise rapidly and make a noise by a strong resilience accumulated in the spring-motor while it is payed out. The decelerator as conventionally used in the roller blind is one among air-damper, oil-damper and fly-wheel type brakes, therefore disadvantageously requiring an accurate adjustment for desired performance.
It is the primary object of the invention to provide such a decelerator for use in roller blinds that is needless to be accurately adjusted for desired performance.
For accomplishment of the object, the decelerator of the invention is used in roller blinds of the type having a spring-motor interposed between a fixed shaft and a tube, and composed of a one-way clutch having the stator thereof secured to the fixed shaft, an epicyclic gearing having a ring gear secured to the inside of the tube, a sun gear, a plurality of planet gears rotatably supported by the rotator of the one-way clutch, and a centrifugal brake having a rotary member secured to the sun gear, centrifugally expansible brake shoes mounted on the rotary member and a brake drum secured to the inside of the tube. The one-way clutch permits the planet gears to rotate about the sun gear with the ring gear or tube in the direction in which the screen is payed out but prevents the planet gears from rotating about the sun gear with the ring gear or tube in the opposite direction. The sun gear or rotary member rotates in the direction opposite to that of the tube at a speed that is a preselected number of times as large as that of the tube when the screen is wound up, so that the brake shoe is forced against the brake drum with a pressure in proportion to the screen-winding speed. The ring gear as well as the brake drum is preferably fixed to the inside of the tube with the intervention of a sound absorbing member in a manner that the screen is quietly wound up.
Other objects and advantages of the invention will in part be obvious and will in part appear hereinafter.